1. Field of the Invention
The present invention relates to a plug used to form a seal for tubes, pipes and similar conduits which transport steam, liquid or gases under pressure and, more particularly, to a plug having an increases degree of expansion to fit larger diameter tubes.
2. Description of the Related Art
In the construction of boilers and other heat exchange equipment, such as those used in the power generation and chemical industries, there is often a need to seal tubes, pipes and similar conduits which transport steam, liquid or gasses under pressure. This sealing is frequently accomplished by the insertion of a plug into the tube. For example, Applicant has disclosed several such plugs in U.S. Pat. Nos. 5,289,851, 6,883,547, and 6,981,524 that, upon insertion, will expand to sealingly engage the inner surface of a boiler or heat exchanger tube. These plugs are limited, however, in their degree of expansion and are thus unable to be used in circumstances where the plug needs to expand a large distance because the plug cannot expand sufficiently without degrading or fracturing, and thus will not properly maintains a seal against leakage of steam, water or other gasses or fluids, over an extended period of time and with a high degree of reliability.